Effective August 2010
Supersedes April 2005
Technical Data TR02800001E
Commonly used
electrical symbols
A one-line diagram is an important means
of communicating the components, electrical
relationships, and connections within a circuit or
system. Components are normally represented
by universally accepted symbols.
The one-line diagram symbols presented here are
commonly accepted symbols. Individual symbols
with an identification and brief explanation and/or
application are presented first. Commonly
accepted combination symbols made up of
individual symbols are also presented in a similar
fashion. For additional information, refer to the
notes on the reverse side.
Table 1. Individual Symbols
Symbol
Identification
Explanation
Transformer
Represents a variety of transformers from liquid-filled to dry-types.
Additional information is normally printed next to symbol indicating
winding connections, primary/secondary voltages, impedance, and
kVA or MVA ratings.
Normally represents a drawout circuit breaker 5 kV and above.
Removable/Drawout
Circuit Breaker
Future Removable/Drawout
Circuit Breaker Position
Non-Drawout Circuit
Breaker
Removable/Drawout
Circuit Breaker
Disconnect Switch
52
Represents a drawout low voltage circuit breaker.
Fuse
Represents a switch in low or high voltage applications
(open position shown).
Represents low voltage and power fuses.
Bus Duct
Represents low and medium voltage bus duct.
Current Transformer
Represents current transformers mounted in assembled equipment.
A ratio of 4000 to 5 amperes shown.
Potential Transformer
Represents potential transformers usually mounted in assembled
equipment. A ratio of 480 to 120 volts shown.
Ground (Earth)
Represents a grounding (earthing) point.
Battery
Represents a battery in an equipment package.
Motor
Represents a motor and also can be shown with an “M” inside the
circle. Additional motor information is commonly printed next to
symbol, such as horsepower, rpm, and voltage.
Can represent a single contact or single-pole switch in the open
position for motor control.
(3)
4000:5
480V
120V
Represents a structure equipped to accept a circuit breaker in the
future, commonly known as provisions.
Represents a fixed mounted low voltage circuit breaker.
Normally Open Contact
Normally Closed Contact
Can represent a single contact or single-pole switch in the closed
position for motor control.
Technical Data TR02800001E
Commonly used 
electrical symbols

Effective August 2010
Symbol
Identification
Explanation
Indicating Light
The letter indicates the color. The color red is indicated.
Overload Relay
Protects a motor should an overload condition develop.
Capacitor
Represents a variety of capacitors.
Ammeter
A letter is usually shown to designate the meter type
(A = ammeter, V = voltmeter, etc.).
The device number designates the relay type (50 = instantaneous
overcurrent, 59 = overvoltage, 86 = lockout, and so on).
The symbol is frequently shown in conjunction with
a transfer switch.
R
A
Instantaneous Overcurrent
Protective Relay
Emergency Generator
50
Table 2. Combination Symbols
Symbol
Identification
Explanation
Fused Disconnect Switch
The symbol is a combination of a fuse and a disconnect switch
with the switch in the open position.
The symbol is a combination of a normally open contact (switch),
overload relay, motor, and disconnect device.
The symbol is a combination of a drawout fuse, normally open
contact (switch), and motor.
A series of circle symbols representing meters usually mounted
in a common enclosure.
Low Voltage Motor Control
Medium Voltage
Motor Starter
Meter Center Enclosure
N
E
or
One circuit breaker representing a main device and other
circuit breakers representing feeder circuits usually in a
common enclosure.
Transfer Switch
Circuit breaker type transfer switch
or
Non-circuit breaker type transfer switch
The instrument connected could be a different instrument
or several different instruments identified by the letter.
Current Transformer with
Connected Ammeter
A
67
Loadcenter or Panelboard
Protective Relays Connected
to Current Transformer
51
Device numbers indicate types of relays connected, such as:
67 = Directional overcurrent
51 = Time overcurrent
NNotes: Some devices, especially new devices, may not have universally
accepted symbols. These devices could be represented in a number of ways,
usually a matter of personal choice. In such instances, the symbol is usually
accompanied by a verbal description. Examples of this situation are:
Addressable
Relay
Universally accepted symbols frequently have additional information
provided near the symbol that distinguishes like symbols from one
another. The following examples are typical:
1200 A
End Cable
Tap Box
In a number of instances, the same symbol can represent a number of
components. They are usually distinguished from one another by letters
or numbers, such as M , W , A , and 50 , representing a motor, watthour
meter, ammeter and overcurrent protective relay, respectively.
225 A/3P
Identifies the drawout circuit breaker represented by the
symbol as a 1200 ampere circuit breaker.
Indicates the fixed circuit breaker represented by the symbol
as a 225 ampere, three-pole breaker.
Indicates that the transformer represented by the symbol is
connected delta-wye.
Eaton Corporation
Electrical Sector
1111 Superior Ave.
Cleveland, OH 44114
United States
877-ETN-CARE (877-386-2273)
Eaton.com
© 2010 Eaton Corporation
All Rights Reserved
Printed in USA
Publication No. TR02800001E / Z10160
August 2010
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